新的5,3‘,5’—三羟基7—甲氧基黄酮及其一二和三苄氧基衍…

通过３．５－二苄氧苯甲酸‘－２，６－二羟基－４－甲氧基苯丙酮酯进行Ｂａｋｅｒ－Ｖｅｎｋａｔａｒａｍａｎ重排，环化合成了５，３’，５’－三苄氧基－７－甲氧基黄酮，然后选择性才全部地脱苄基得到５，３’，５’－三羟基－７－甲氧基黄酮及其一和二－苄基衍生物。     

TDF对~（60）Co－γ线诱发淋巴细胞微核发生率的影响

ＴＤＦ（５，３′，５′－三羟基－７－甲氧基，二氢黄酮）能抑制~（６０）Ｃｏ－γ射线低剂量所引起的人离体外周血淋巴细胞的微核发生率，助溶剂ＤＭＳｏ无明显的抑制作用。     

4－羟基－3，5－二溴苄叉绕丹宁分光光度法测定银（Ⅰ）

本文提出了新显色剂４－羟基－３，５－二溴苄叉绕丹宁测定银（Ｉ）的分光光度方法．在ｐＨ１２，聚乙二醇－４００存在下，银（Ｉ）与４－羟基－３，５－二溴苄叉绕丹宁形成１：２深红色络合物，其最大吸收波长在５１０ｎｍ，并且在室温下可稳定存在２４小时以上．在２５ｍＬ容积中，Ａｇ￣＋在０～１００μｇ范围符合比尔定律，摩尔吸光系数为１．１５×１０￣４Ｌ·ｍｏＬ￣（－ｌ）·ｃｍ￣（－１），标准偏差为０．００３（ｎ＝１０）．     

（1R，3R）－（－）－1－甲氧基－5，6－亚甲二氧基－3－（3，4，5－三甲氧苯基）－异苯并二氢呋喃的选择性合成

在ＬｉＡｌＨ４及光学活性物质（５Ｒ）－孟氧基－２（５Ｈ）－呋喃酮（５）存在下，将６－（３′，４′，５′－三甲氧基羟卞基）－胡椒醛二甲缩醛（４）的甲苯溶液加热回流８小时，可得旋光性的（１Ｒ，３Ｒ）－（－）－１－甲氧基－５，６－亚甲二氧基－３－（３，４，５－三甲氧苯基）－异苯并二氢呋喃晶体（１），产率６１．８％．     

4，4－二氯－8，11－二甲氧基三环［5，4，0，0~（3，5）］十一碳－7，9，11－三烯的合成及光谱性质

本文报导４，４－二氯－８，１１－二甲氧基三环［５，４，０，０~（３，５）］十一碳－７，９，１１－三烯的合成．用元素分析确定其分子组成为Ｃ_（１３）Ｈ_（１４）Ｏ_２Ｃｌ_２．测定并讨论其质谱，~１Ｈ和~（１３）Ｃ核磁共振谱．     

3，4，5－三甲氧基苯甲醛的合成

３，４，５－三甲氧苯甲醛是制ＴＭＰ的关键中间体，用苯酚先磺化再溴化，再经甲氧基化、甲酰化、甲基化４步反应合成。每步产率分别为７７．７％，７６．０％，４１．０％和９３．０％，总收率为２２．５％。对２，６－二甲氧基苯酚的Ｖｉｌｓｍｅｉｅｒ－Ｈａａｃｋ甲酰化反应，Ｄｕｆｆ反应以及Ｒｅｉｍｅｒ－Ｔｉｅｍａｎｎ反应等可能的甲酰化方法进行了研究。     

西松烯内酯的合成研究Ⅲ．苏式－7，14－二羟基－3，9，13－三甲基－6－异丙烯基－（2E，8E，12E）－十四碳三烯苯硫醚的合成

本文报道苏式－７，１４－二羟基－３，９，１３－三甲基－６－异丙烯基－（２Ｅ，８Ｅ，１２Ｅ）－十四碳三烯苯硫醚（８）的２条合成路线，路线１以溴化物（３）和牛儿醛为原料，经缩合，基团保护、氧化和去保护基四步反应合成（８），总产率２４％，路线２则经氧化和缩合两步反应得到（８），总产率４８％。     

华荠薴中的黄酮类化合物

从华荠（ＭｏｓｌａｃｈｉｎｅｎｓｉｓＭａｘｉｍ）中分离鉴定了６种黄酮类化合物，经光谱分析及化学方法鉴定为：５－羟基－６，７－甲基黄酮；５，７－二羟基－４＇－甲氧基黄酮；洋芹素；鼠李柠檬素；桑色素－７－Ｏ－β－Ｄ－葡萄糖甙；山奈素－３－Ｏ－β－Ｄ－葡萄糖甙．均为首次从该植物中分得．     

选择性去甲醚化反应—3，5—二甲氧基4—羟基甲苯甲酸甲酯的新合成方法

报道利用复合试剂无水氯化锌和丙酸可选择性地脱去3,4,5－三甲氧基4－羟基苯甲酸甲酯的4位甲氧基,较高收率的得到3,5－二甲氧基4－羟基苯甲酸甲酯。     

稀土Nd、Eu氯化物与4＇，5＇－二溴苯并15－冠－5固体配合物的合成及性质

以无水乙腈为溶剂，合成了Ｎｄ、Ｅｕ氯化物与４＇，５＇－二溴苯并１５－冠－５的固体配合物，进行了元素分析、红外先谱、紫外光谱及在尔电导的测定；结果表明配合物的组成为１：２型电解质．     

2，2＇，5，5＇－四氯联苯胺的电解合成

本文论述了电解法将２，５－二氯硝基苯还原为四氯氢化偶氮苯，进而转位、重排生成２，２＇，５，５＇－四氯联苯胺的原理、工艺条件及实验方法     

Why do nucleic acids have 3'5' phosphodiester bonds?

Details of the stereochemistry of the 2'5' and 3'5' dinucleoside monophosphates of polynucleotides have been delineated in aqueous solution using nuclear magnetic resonance spectroscopy. Incorporation of these experimentally determined geometries into the structure of polynucleotides reveals that the intrinsic spatial configurations of the 2'5' bonds cannot support helical structures whereas the geometries of 3'5' bonds allow the formation of helical configurations for RNA.     

类黄酮3′，5′羟基化酶基因的克隆及转化矮牵牛

类黄酮3′,5′羟基化酶(Flavonoid 3′,5′-hydroxylase,F3′,5′H)是花色素苷代谢途径中的一个关键酶,它使花色素的合成方向趋向于形成蓝色色素翠雀素。利用PCR方法,从“紫蓝色”品系的矮牵牛(Petunia hybrida)总DNA中,克隆到编码F3′,5′H的Hf1、Hf2基因。将Hf2基因正向插入到植物表达中间载体中,通过土壤农杆菌介导的方法转化“淡粉色”品系的矮牵牛。现已得到PCR阳性植株。     

5'-Terminal 7-methylguanosine in eukaryotic mRNA is required for translation.

Unmethylated reovirus and VSV mRNAs are specifically methylated to form 5'-terminal structures of the type, m-7-G(5')ppp(5')N by protein synthesising extracts prepared from wheat germ and mouse L cells. Reticulocyte mRNA also contains 5'-terminal m-7-G. MRNAs having 5'-terminal m-7-G stimulate protein synthesis in vitro. Removal of m-7-G by beta-elimination abolishes translation of the mRNAs.     

Cleavage of 5' splice site and lariat formation are independent of 3' splice site in yeast mRNA splicing

Analysis of messenger RNA splicing in yeast and in metazoa has led to the identification of an RNA molecule in a lariat conformation. This structure has been found as an mRNA splicing intermediate in vitro and identical molecules have been identified in vivo. Lariat formation involves cleavage of the precursor at the 5' splice site (5' SS) and the formation of a 2'-5' phosphodiester bond between the guanosine residue at the 5' end of the intron and an adenosine within the intron. The yeast branchpoint is located within the absolutely conserved TACTAAC box (that is, the last A of the TACTAAC box is the site of formation of the 2'-5' phosphodiester bond with the 5' end of the intron)3,4. Moreover, efficient 5' SS cleavage and lariat formation require proper sequences at the 5' splice junction and within the TACTAAC box. Here we demonstrate that 5' SS cleavage and lariat formation take place in vitro in the absence of the 3' SS and much of the 3' junction. These results are discussed in light of possible differences between yeast and metazoan mRNA splicing.     

Dicer recognizes the 5' end of RNA for efficient and accurate processing

A hallmark of RNA silencing is a class of approximately 22-nucleotide RNAs that are processed from double-stranded RNA precursors by Dicer. Accurate processing by Dicer is crucial for the functionality of microRNAs (miRNAs). The current model posits that Dicer selects cleavage sites by measuring a set distance from the 3' overhang of the double-stranded RNA terminus. Here we report that human Dicer anchors not only the 3' end but also the 5' end, with the cleavage site determined mainly by the distance (～22 nucleotides) from the 5' end (5' counting rule). This cleavage requires a 5'-terminal phosphate group. Further, we identify a novel basic motif (5' pocket) in human Dicer that recognizes the 5'-phosphorylated end. The 5' counting rule and the 5' anchoring residues are conserved in Drosophila Dicer-1, but not in Giardia Dicer. Mutations in the 5' pocket reduce processing efficiency and alter cleavage sites in vitro. Consistently, miRNA biogenesis is perturbed in vivo when Dicer-null embryonic stem cells are replenished with the 5'-pocket mutant. Thus, 5'-end recognition by Dicer is important for precise and effective biogenesis of miRNAs. Insights from this study should also afford practical benefits to the design of small hairpin RNAs.     

Mechanism of recognition of the 5' splice site in self-splicing group I introns

Group I introns include many mitochondrial ribosomal RNA and messenger RNA introns and the nuclear rRNA introns of Tetrahymena and Physarum. The splicing of precursor RNAs containing these introns is a two-step reaction. Cleavage at the 5' splice site precedes cleavage at the 3' splice site, the latter cleavage being coupled with exon ligation. Following the first cleavage, the 5' exon must somehow be held in place for ligation. We have now tested the reactivity of two self-splicing group I RNAs, the Tetrahymena pre-rRNA and the intron 1 portion of the Neurospora mitochondrial cytochrome b (cob) pre-mRNA, in the intermolecular exon ligation reaction (splicing in trans) described by Inoue et al. The different sequence specificity of the reactions supports the idea that the nucleotides immediately upstream from the 5' splice site are base-paired to an internal, 5' exon-binding site, in agreement with RNA structure models proposed by Davies and co-workers and others. The internal binding site is proposed to be involved in the formation of a structure that specifies the 5' splice site and, following the first step of splicing, to hold the 5' exon in place for exon ligation.     

2'5' oligo(A) polymerase activity in serum of mice infected with EMC virus or treated with interferon

Interferon-treated cells show an increase in two double-stranded RNA (dsRNA)-dependent enzymatic activities involving an oligoadenylate polymerase and a protein kinase (ref. 1 and refs therein). The polymerase converts ATP into a series of oligonucleotides characterized by 2'5'-phosphodiester bonds, designated 2'5'-oligo(A) or 2-5A (ref. 1). These oligonucleotides activate an endoribonuclease that degrades RNA in extracts of control and interferon-treated cells. These observations have been made in tissue culture cells and no informatin is yet available on these enzymatic activities in animals with elevated interferon levels. We report here on 2-5A synthesis in tissue homogenates and serum of mice infected with encephalomyocarditis virus (EMCV); this virus induces interferon synthesis when injected intraperitoneally into mice. Significant synthesis of 2-5A was detected in extracts of spleen and lungs, but also, surprisingly, in the serum of these mice. Subsequent experiments showed synthesis of 2-5A in serum of mice treated with the interferon inducer poly(I) x poly(C) (ref. 3) or with mouse fibroblast interferon.